// SPDX-License-Identifier: GPL-2.0-or-later
/*****************************************************************************
 * Linux PPP over L2TP (PPPoX/PPPoL2TP) Sockets
 *
 * PPPoX    --- Generic PPP encapsulation socket family
 * PPPoL2TP --- PPP over L2TP (RFC 2661)
 *
 * Version:     2.0.0
 *
 * Authors:     James Chapman (jchapman@katalix.com)
 *
 * Based on original work by Martijn van Oosterhout <kleptog@svana.org>
 *
 * License:
 */

/* This driver handles only L2TP data frames; control frames are handled by a
 * userspace application.
 *
 * To send data in an L2TP session, userspace opens a PPPoL2TP socket and
 * attaches it to a bound UDP socket with local tunnel_id / session_id and
 * peer tunnel_id / session_id set. Data can then be sent or received using
 * regular socket sendmsg() / recvmsg() calls. Kernel parameters of the socket
 * can be read or modified using ioctl() or [gs]etsockopt() calls.
 *
 * When a PPPoL2TP socket is connected with local and peer session_id values
 * zero, the socket is treated as a special tunnel management socket.
 *
 * Here's example userspace code to create a socket for sending/receiving data
 * over an L2TP session:-
 *
 *      struct sockaddr_pppol2tp sax;
 *      int fd;
 *      int session_fd;
 *
 *      fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
 *
 *      sax.sa_family = AF_PPPOX;
 *      sax.sa_protocol = PX_PROTO_OL2TP;
 *      sax.pppol2tp.fd = tunnel_fd;    // bound UDP socket
 *      sax.pppol2tp.addr.sin_addr.s_addr = addr->sin_addr.s_addr;
 *      sax.pppol2tp.addr.sin_port = addr->sin_port;
 *      sax.pppol2tp.addr.sin_family = AF_INET;
 *      sax.pppol2tp.s_tunnel  = tunnel_id;
 *      sax.pppol2tp.s_session = session_id;
 *      sax.pppol2tp.d_tunnel  = peer_tunnel_id;
 *      sax.pppol2tp.d_session = peer_session_id;
 *
 *      session_fd = connect(fd, (struct sockaddr *)&sax, sizeof(sax));
 *
 * A pppd plugin that allows PPP traffic to be carried over L2TP using
 * this driver is available from the OpenL2TP project at
 * http://openl2tp.sourceforge.net.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/uaccess.h>

#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/jiffies.h>

#include <linux/netdevice.h>
#include <linux/net.h>
#include <linux/inetdevice.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/if_pppox.h>
#include <linux/if_pppol2tp.h>
#include <net/sock.h>
#include <linux/ppp_channel.h>
#include <linux/ppp_defs.h>
#include <linux/ppp-ioctl.h>
#include <linux/file.h>
#include <linux/hash.h>
#include <linux/sort.h>
#include <linux/proc_fs.h>
#include <linux/l2tp.h>
#include <linux/nsproxy.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/inet_common.h>

#include <asm/byteorder.h>
#include <linux/atomic.h>

#include "l2tp_core.h"

#define PPPOL2TP_DRV_VERSION    "V2.0"

/* Space for UDP, L2TP and PPP headers */
#define PPPOL2TP_HEADER_OVERHEAD        40

/* Number of bytes to build transmit L2TP headers.
 * Unfortunately the size is different depending on whether sequence numbers
 * are enabled.
 */
#define PPPOL2TP_L2TP_HDR_SIZE_SEQ              10
#define PPPOL2TP_L2TP_HDR_SIZE_NOSEQ            6

/* Private data of each session. This data lives at the end of struct
 * l2tp_session, referenced via session->priv[].
 */
struct pppol2tp_session {
        int                     owner;          /* pid that opened the socket */

        struct mutex            sk_lock;        /* Protects .sk */
        struct sock __rcu       *sk;            /* Pointer to the session PPPoX socket */
        struct sock             *__sk;          /* Copy of .sk, for cleanup */
};

static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb);

static const struct ppp_channel_ops pppol2tp_chan_ops = {
        .start_xmit =  pppol2tp_xmit,
};

static const struct proto_ops pppol2tp_ops;

/* Retrieves the pppol2tp socket associated to a session. */
static struct sock *pppol2tp_session_get_sock(struct l2tp_session *session)
{
        struct pppol2tp_session *ps = l2tp_session_priv(session);

        return rcu_dereference(ps->sk);
}

/* Helpers to obtain tunnel/session contexts from sockets.
 */
static struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
{
        struct l2tp_session *session;

        if (!sk)
                return NULL;

        rcu_read_lock();
        session = rcu_dereference_sk_user_data(sk);
        if (session && refcount_inc_not_zero(&session->ref_count)) {
                rcu_read_unlock();
                WARN_ON_ONCE(session->magic != L2TP_SESSION_MAGIC);
                return session;
        }
        rcu_read_unlock();

        return NULL;
}

/*****************************************************************************
 * Receive data handling
 *****************************************************************************/

/* Receive message. This is the recvmsg for the PPPoL2TP socket.
 */
static int pppol2tp_recvmsg(struct socket *sock, struct msghdr *msg,
                            size_t len, int flags)
{
        int err;
        struct sk_buff *skb;
        struct sock *sk = sock->sk;

        err = -EIO;
        if (sk->sk_state & PPPOX_BOUND)
                goto end;

        err = 0;
        skb = skb_recv_datagram(sk, flags, &err);
        if (!skb)
                goto end;

        if (len > skb->len)
                len = skb->len;
        else if (len < skb->len)
                msg->msg_flags |= MSG_TRUNC;

        err = skb_copy_datagram_msg(skb, 0, msg, len);
        if (likely(err == 0))
                err = len;

        kfree_skb(skb);
end:
        return err;
}

static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int data_len)
{
        struct sock *sk;

        /* If the socket is bound, send it in to PPP's input queue. Otherwise
         * queue it on the session socket.
         */
        rcu_read_lock();
        sk = pppol2tp_session_get_sock(session);
        if (!sk)
                goto no_sock;

        /* If the first two bytes are 0xFF03, consider that it is the PPP's
         * Address and Control fields and skip them. The L2TP module has always
         * worked this way, although, in theory, the use of these fields should
         * be negotiated and handled at the PPP layer. These fields are
         * constant: 0xFF is the All-Stations Address and 0x03 the Unnumbered
         * Information command with Poll/Final bit set to zero (RFC 1662).
         */
        if (pskb_may_pull(skb, 2) && skb->data[0] == PPP_ALLSTATIONS &&
            skb->data[1] == PPP_UI)
                skb_pull(skb, 2);

        if (sk->sk_state & PPPOX_BOUND) {
                struct pppox_sock *po;

                po = pppox_sk(sk);
                ppp_input(&po->chan, skb);
        } else {
                if (sock_queue_rcv_skb(sk, skb) < 0) {
                        atomic_long_inc(&session->stats.rx_errors);
                        kfree_skb(skb);
                }
        }
        rcu_read_unlock();

        return;

no_sock:
        rcu_read_unlock();
        pr_warn_ratelimited("%s: no socket in recv\n", session->name);
        kfree_skb(skb);
}

/************************************************************************
 * Transmit handling
 ***********************************************************************/

/* This is the sendmsg for the PPPoL2TP pppol2tp_session socket.  We come here
 * when a user application does a sendmsg() on the session socket. L2TP and
 * PPP headers must be inserted into the user's data.
 */
static int pppol2tp_sendmsg(struct socket *sock, struct msghdr *m,
                            size_t total_len)
{
        struct sock *sk = sock->sk;
        struct sk_buff *skb;
        int error;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int uhlen;

        error = -ENOTCONN;
        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                goto error;

        /* Get session and tunnel contexts */
        error = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (!session)
                goto error;

        tunnel = session->tunnel;

        uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;

        /* Allocate a socket buffer */
        error = -ENOMEM;
        skb = sock_wmalloc(sk, NET_SKB_PAD + sizeof(struct iphdr) +
                           uhlen + session->hdr_len +
                           2 + total_len, /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
                           0, GFP_KERNEL);
        if (!skb)
                goto error_put_sess;

        /* Reserve space for headers. */
        skb_reserve(skb, NET_SKB_PAD);
        skb_reset_network_header(skb);
        skb_reserve(skb, sizeof(struct iphdr));
        skb_reset_transport_header(skb);
        skb_reserve(skb, uhlen);

        /* Add PPP header */
        skb->data[0] = PPP_ALLSTATIONS;
        skb->data[1] = PPP_UI;
        skb_put(skb, 2);

        /* Copy user data into skb */
        error = memcpy_from_msg(skb_put(skb, total_len), m, total_len);
        if (error < 0) {
                kfree_skb(skb);
                goto error_put_sess;
        }

        local_bh_disable();
        l2tp_xmit_skb(session, skb);
        local_bh_enable();

        l2tp_session_put(session);

        return total_len;

error_put_sess:
        l2tp_session_put(session);
error:
        return error;
}

/* Transmit function called by generic PPP driver.  Sends PPP frame
 * over PPPoL2TP socket.
 *
 * This is almost the same as pppol2tp_sendmsg(), but rather than
 * being called with a msghdr from userspace, it is called with a skb
 * from the kernel.
 *
 * The supplied skb from ppp doesn't have enough headroom for the
 * insertion of L2TP, UDP and IP headers so we need to allocate more
 * headroom in the skb. This will create a cloned skb. But we must be
 * careful in the error case because the caller will expect to free
 * the skb it supplied, not our cloned skb. So we take care to always
 * leave the original skb unfreed if we return an error.
 */
static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
{
        struct sock *sk = (struct sock *)chan->private;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int uhlen, headroom;

        if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                goto abort;

        /* Get session and tunnel contexts from the socket */
        session = pppol2tp_sock_to_session(sk);
        if (!session)
                goto abort;

        tunnel = session->tunnel;

        uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
        headroom = NET_SKB_PAD +
                   sizeof(struct iphdr) + /* IP header */
                   uhlen +              /* UDP header (if L2TP_ENCAPTYPE_UDP) */
                   session->hdr_len +   /* L2TP header */
                   2;                   /* 2 bytes for PPP_ALLSTATIONS & PPP_UI */
        if (skb_cow_head(skb, headroom))
                goto abort_put_sess;

        /* Setup PPP header */
        __skb_push(skb, 2);
        skb->data[0] = PPP_ALLSTATIONS;
        skb->data[1] = PPP_UI;

        local_bh_disable();
        l2tp_xmit_skb(session, skb);
        local_bh_enable();

        l2tp_session_put(session);

        return 1;

abort_put_sess:
        l2tp_session_put(session);
abort:
        /* Free the original skb */
        kfree_skb(skb);
        return 1;
}

/*****************************************************************************
 * Session (and tunnel control) socket create/destroy.
 *****************************************************************************/

/* Really kill the session socket. (Called from sock_put() if
 * refcnt == 0.)
 */
static void pppol2tp_session_destruct(struct sock *sk)
{
        skb_queue_purge(&sk->sk_receive_queue);
        skb_queue_purge(&sk->sk_write_queue);
}

static void pppol2tp_session_close(struct l2tp_session *session)
{
        struct pppol2tp_session *ps;

        ps = l2tp_session_priv(session);
        mutex_lock(&ps->sk_lock);
        ps->__sk = rcu_dereference_protected(ps->sk,
                                             lockdep_is_held(&ps->sk_lock));
        RCU_INIT_POINTER(ps->sk, NULL);
        mutex_unlock(&ps->sk_lock);
        if (ps->__sk) {
                /* detach socket */
                rcu_assign_sk_user_data(ps->__sk, NULL);
                sock_put(ps->__sk);

                /* drop ref taken when we referenced socket via sk_user_data */
                l2tp_session_put(session);
        }
}

/* Called when the PPPoX socket (session) is closed.
 */
static int pppol2tp_release(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        int error;

        if (!sk)
                return 0;

        error = -EBADF;
        lock_sock(sk);
        if (sock_flag(sk, SOCK_DEAD) != 0)
                goto error;

        pppox_unbind_sock(sk);

        /* Signal the death of the socket. */
        sk->sk_state = PPPOX_DEAD;
        sock_orphan(sk);
        sock->sk = NULL;

        session = pppol2tp_sock_to_session(sk);
        if (session) {
                l2tp_session_delete(session);
                /* drop ref taken by pppol2tp_sock_to_session */
                l2tp_session_put(session);
        }

        release_sock(sk);

        sock_put(sk);

        return 0;

error:
        release_sock(sk);
        return error;
}

static struct proto pppol2tp_sk_proto = {
        .name     = "PPPOL2TP",
        .owner    = THIS_MODULE,
        .obj_size = sizeof(struct pppox_sock),
};

static int pppol2tp_backlog_recv(struct sock *sk, struct sk_buff *skb)
{
        int rc;

        rc = l2tp_udp_encap_recv(sk, skb);
        if (rc)
                kfree_skb(skb);

        return NET_RX_SUCCESS;
}

/* socket() handler. Initialize a new struct sock.
 */
static int pppol2tp_create(struct net *net, struct socket *sock, int kern)
{
        int error = -ENOMEM;
        struct sock *sk;

        sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pppol2tp_sk_proto, kern);
        if (!sk)
                goto out;

        sock_init_data(sock, sk);
        sock_set_flag(sk, SOCK_RCU_FREE);

        sock->state  = SS_UNCONNECTED;
        sock->ops    = &pppol2tp_ops;

        sk->sk_backlog_rcv = pppol2tp_backlog_recv;
        sk->sk_protocol    = PX_PROTO_OL2TP;
        sk->sk_family      = PF_PPPOX;
        sk->sk_state       = PPPOX_NONE;
        sk->sk_type        = SOCK_STREAM;
        sk->sk_destruct    = pppol2tp_session_destruct;

        error = 0;

out:
        return error;
}

static void pppol2tp_show(struct seq_file *m, void *arg)
{
        struct l2tp_session *session = arg;
        struct sock *sk;

        rcu_read_lock();
        sk = pppol2tp_session_get_sock(session);
        if (sk) {
                struct pppox_sock *po = pppox_sk(sk);

                seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
        }
        rcu_read_unlock();
}

static void pppol2tp_session_init(struct l2tp_session *session)
{
        struct pppol2tp_session *ps;

        session->recv_skb = pppol2tp_recv;
        session->session_close = pppol2tp_session_close;
        if (IS_ENABLED(CONFIG_L2TP_DEBUGFS))
                session->show = pppol2tp_show;

        ps = l2tp_session_priv(session);
        mutex_init(&ps->sk_lock);
        ps->owner = current->pid;
}

struct l2tp_connect_info {
        u8 version;
        int fd;
        u32 tunnel_id;
        u32 peer_tunnel_id;
        u32 session_id;
        u32 peer_session_id;
};

static int pppol2tp_sockaddr_get_info(const void *sa, int sa_len,
                                      struct l2tp_connect_info *info)
{
        switch (sa_len) {
        case sizeof(struct sockaddr_pppol2tp):
        {
                const struct sockaddr_pppol2tp *sa_v2in4 = sa;

                if (sa_v2in4->sa_protocol != PX_PROTO_OL2TP)
                        return -EINVAL;

                info->version = 2;
                info->fd = sa_v2in4->pppol2tp.fd;
                info->tunnel_id = sa_v2in4->pppol2tp.s_tunnel;
                info->peer_tunnel_id = sa_v2in4->pppol2tp.d_tunnel;
                info->session_id = sa_v2in4->pppol2tp.s_session;
                info->peer_session_id = sa_v2in4->pppol2tp.d_session;

                break;
        }
        case sizeof(struct sockaddr_pppol2tpv3):
        {
                const struct sockaddr_pppol2tpv3 *sa_v3in4 = sa;

                if (sa_v3in4->sa_protocol != PX_PROTO_OL2TP)
                        return -EINVAL;

                info->version = 3;
                info->fd = sa_v3in4->pppol2tp.fd;
                info->tunnel_id = sa_v3in4->pppol2tp.s_tunnel;
                info->peer_tunnel_id = sa_v3in4->pppol2tp.d_tunnel;
                info->session_id = sa_v3in4->pppol2tp.s_session;
                info->peer_session_id = sa_v3in4->pppol2tp.d_session;

                break;
        }
        case sizeof(struct sockaddr_pppol2tpin6):
        {
                const struct sockaddr_pppol2tpin6 *sa_v2in6 = sa;

                if (sa_v2in6->sa_protocol != PX_PROTO_OL2TP)
                        return -EINVAL;

                info->version = 2;
                info->fd = sa_v2in6->pppol2tp.fd;
                info->tunnel_id = sa_v2in6->pppol2tp.s_tunnel;
                info->peer_tunnel_id = sa_v2in6->pppol2tp.d_tunnel;
                info->session_id = sa_v2in6->pppol2tp.s_session;
                info->peer_session_id = sa_v2in6->pppol2tp.d_session;

                break;
        }
        case sizeof(struct sockaddr_pppol2tpv3in6):
        {
                const struct sockaddr_pppol2tpv3in6 *sa_v3in6 = sa;

                if (sa_v3in6->sa_protocol != PX_PROTO_OL2TP)
                        return -EINVAL;

                info->version = 3;
                info->fd = sa_v3in6->pppol2tp.fd;
                info->tunnel_id = sa_v3in6->pppol2tp.s_tunnel;
                info->peer_tunnel_id = sa_v3in6->pppol2tp.d_tunnel;
                info->session_id = sa_v3in6->pppol2tp.s_session;
                info->peer_session_id = sa_v3in6->pppol2tp.d_session;

                break;
        }
        default:
                return -EINVAL;
        }

        return 0;
}

/* Rough estimation of the maximum payload size a tunnel can transmit without
 * fragmenting at the lower IP layer. Assumes L2TPv2 with sequence
 * numbers and no IP option. Not quite accurate, but the result is mostly
 * unused anyway.
 */
static int pppol2tp_tunnel_mtu(const struct l2tp_tunnel *tunnel)
{
        int mtu;

        mtu = l2tp_tunnel_dst_mtu(tunnel);
        if (mtu <= PPPOL2TP_HEADER_OVERHEAD)
                return 1500 - PPPOL2TP_HEADER_OVERHEAD;

        return mtu - PPPOL2TP_HEADER_OVERHEAD;
}

static struct l2tp_tunnel *pppol2tp_tunnel_get(struct net *net,
                                               const struct l2tp_connect_info *info,
                                               bool *new_tunnel)
{
        struct l2tp_tunnel *tunnel;
        int error;

        *new_tunnel = false;

        tunnel = l2tp_tunnel_get(net, info->tunnel_id);

        /* Special case: create tunnel context if session_id and
         * peer_session_id is 0. Otherwise look up tunnel using supplied
         * tunnel id.
         */
        if (!info->session_id && !info->peer_session_id) {
                if (!tunnel) {
                        struct l2tp_tunnel_cfg tcfg = {
                                .encap = L2TP_ENCAPTYPE_UDP,
                        };

                        /* Prevent l2tp_tunnel_register() from trying to set up
                         * a kernel socket.
                         */
                        if (info->fd < 0)
                                return ERR_PTR(-EBADF);

                        error = l2tp_tunnel_create(info->fd,
                                                   info->version,
                                                   info->tunnel_id,
                                                   info->peer_tunnel_id, &tcfg,
                                                   &tunnel);
                        if (error < 0)
                                return ERR_PTR(error);

                        refcount_inc(&tunnel->ref_count);
                        error = l2tp_tunnel_register(tunnel, net, &tcfg);
                        if (error < 0) {
                                kfree(tunnel);
                                return ERR_PTR(error);
                        }

                        *new_tunnel = true;
                }
        } else {
                /* Error if we can't find the tunnel */
                if (!tunnel)
                        return ERR_PTR(-ENOENT);

                /* Error if socket is not prepped */
                if (!tunnel->sock) {
                        l2tp_tunnel_put(tunnel);
                        return ERR_PTR(-ENOENT);
                }
        }

        return tunnel;
}

/* connect() handler. Attach a PPPoX socket to a tunnel UDP socket
 */
static int pppol2tp_connect(struct socket *sock, struct sockaddr_unsized *uservaddr,
                            int sockaddr_len, int flags)
{
        struct sock *sk = sock->sk;
        struct pppox_sock *po = pppox_sk(sk);
        struct l2tp_session *session = NULL;
        struct l2tp_connect_info info;
        struct l2tp_tunnel *tunnel;
        struct pppol2tp_session *ps;
        struct l2tp_session_cfg cfg = { 0, };
        bool drop_refcnt = false;
        bool new_session = false;
        bool new_tunnel = false;
        int error;

        error = pppol2tp_sockaddr_get_info(uservaddr, sockaddr_len, &info);
        if (error < 0)
                return error;

        /* Don't bind if tunnel_id is 0 */
        if (!info.tunnel_id)
                return -EINVAL;

        tunnel = pppol2tp_tunnel_get(sock_net(sk), &info, &new_tunnel);
        if (IS_ERR(tunnel))
                return PTR_ERR(tunnel);

        lock_sock(sk);

        /* Check for already bound sockets */
        error = -EBUSY;
        if (sk->sk_state & PPPOX_CONNECTED)
                goto end;

        /* We don't supporting rebinding anyway */
        error = -EALREADY;
        if (sk->sk_user_data)
                goto end; /* socket is already attached */

        if (tunnel->peer_tunnel_id == 0)
                tunnel->peer_tunnel_id = info.peer_tunnel_id;

        session = l2tp_session_get(sock_net(sk), tunnel->sock, tunnel->version,
                                   info.tunnel_id, info.session_id);
        if (session) {
                drop_refcnt = true;

                if (session->pwtype != L2TP_PWTYPE_PPP) {
                        error = -EPROTOTYPE;
                        goto end;
                }

                ps = l2tp_session_priv(session);

                /* Using a pre-existing session is fine as long as it hasn't
                 * been connected yet.
                 */
                mutex_lock(&ps->sk_lock);
                if (rcu_dereference_protected(ps->sk,
                                              lockdep_is_held(&ps->sk_lock)) ||
                    ps->__sk) {
                        mutex_unlock(&ps->sk_lock);
                        error = -EEXIST;
                        goto end;
                }
        } else {
                cfg.pw_type = L2TP_PWTYPE_PPP;

                session = l2tp_session_create(sizeof(struct pppol2tp_session),
                                              tunnel, info.session_id,
                                              info.peer_session_id, &cfg);
                if (IS_ERR(session)) {
                        error = PTR_ERR(session);
                        goto end;
                }

                drop_refcnt = true;

                pppol2tp_session_init(session);
                ps = l2tp_session_priv(session);
                refcount_inc(&session->ref_count);

                mutex_lock(&ps->sk_lock);
                error = l2tp_session_register(session, tunnel);
                if (error < 0) {
                        mutex_unlock(&ps->sk_lock);
                        l2tp_session_put(session);
                        goto end;
                }

                new_session = true;
        }

        /* Special case: if source & dest session_id == 0x0000, this
         * socket is being created to manage the tunnel. Just set up
         * the internal context for use by ioctl() and sockopt()
         * handlers.
         */
        if (session->session_id == 0 && session->peer_session_id == 0) {
                error = 0;
                goto out_no_ppp;
        }

        /* The only header we need to worry about is the L2TP
         * header. This size is different depending on whether
         * sequence numbers are enabled for the data channel.
         */
        po->chan.hdrlen = PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;

        po->chan.private = sk;
        po->chan.ops     = &pppol2tp_chan_ops;
        po->chan.mtu     = pppol2tp_tunnel_mtu(tunnel);
        po->chan.direct_xmit    = true;

        error = ppp_register_net_channel(sock_net(sk), &po->chan);
        if (error) {
                mutex_unlock(&ps->sk_lock);
                goto end;
        }

out_no_ppp:
        /* This is how we get the session context from the socket. */
        sock_hold(sk);
        rcu_assign_sk_user_data(sk, session);
        rcu_assign_pointer(ps->sk, sk);
        mutex_unlock(&ps->sk_lock);

        /* Keep the reference we've grabbed on the session: sk doesn't expect
         * the session to disappear. pppol2tp_session_close() is responsible
         * for dropping it.
         */
        drop_refcnt = false;

        sk->sk_state = PPPOX_CONNECTED;

end:
        if (error) {
                if (new_session)
                        l2tp_session_delete(session);
                if (new_tunnel)
                        l2tp_tunnel_delete(tunnel);
        }
        if (drop_refcnt)
                l2tp_session_put(session);
        l2tp_tunnel_put(tunnel);
        release_sock(sk);

        return error;
}

#ifdef CONFIG_L2TP_V3

/* Called when creating sessions via the netlink interface. */
static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel,
                                   u32 session_id, u32 peer_session_id,
                                   struct l2tp_session_cfg *cfg)
{
        int error;
        struct l2tp_session *session;

        /* Error if tunnel socket is not prepped */
        if (!tunnel->sock) {
                error = -ENOENT;
                goto err;
        }

        /* Allocate and initialize a new session context. */
        session = l2tp_session_create(sizeof(struct pppol2tp_session),
                                      tunnel, session_id,
                                      peer_session_id, cfg);
        if (IS_ERR(session)) {
                error = PTR_ERR(session);
                goto err;
        }

        pppol2tp_session_init(session);

        error = l2tp_session_register(session, tunnel);
        if (error < 0)
                goto err_sess;

        return 0;

err_sess:
        l2tp_session_put(session);
err:
        return error;
}

#endif /* CONFIG_L2TP_V3 */

/* getname() support.
 */
static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
                            int peer)
{
        int len = 0;
        int error = 0;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        struct sock *sk = sock->sk;
        struct inet_sock *inet;
        struct pppol2tp_session *pls;

        error = -ENOTCONN;
        if (!sk)
                goto end;
        if (!(sk->sk_state & PPPOX_CONNECTED))
                goto end;

        error = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (!session)
                goto end;

        pls = l2tp_session_priv(session);
        tunnel = session->tunnel;

        inet = inet_sk(tunnel->sock);
        if (tunnel->version == 2 && tunnel->sock->sk_family == AF_INET) {
                struct sockaddr_pppol2tp sp;

                len = sizeof(sp);
                memset(&sp, 0, len);
                sp.sa_family    = AF_PPPOX;
                sp.sa_protocol  = PX_PROTO_OL2TP;
                sp.pppol2tp.fd  = tunnel->fd;
                sp.pppol2tp.pid = pls->owner;
                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
                sp.pppol2tp.s_session = session->session_id;
                sp.pppol2tp.d_session = session->peer_session_id;
                sp.pppol2tp.addr.sin_family = AF_INET;
                sp.pppol2tp.addr.sin_port = inet->inet_dport;
                sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
                memcpy(uaddr, &sp, len);
#if IS_ENABLED(CONFIG_IPV6)
        } else if (tunnel->version == 2 && tunnel->sock->sk_family == AF_INET6) {
                struct sockaddr_pppol2tpin6 sp;

                len = sizeof(sp);
                memset(&sp, 0, len);
                sp.sa_family    = AF_PPPOX;
                sp.sa_protocol  = PX_PROTO_OL2TP;
                sp.pppol2tp.fd  = tunnel->fd;
                sp.pppol2tp.pid = pls->owner;
                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
                sp.pppol2tp.s_session = session->session_id;
                sp.pppol2tp.d_session = session->peer_session_id;
                sp.pppol2tp.addr.sin6_family = AF_INET6;
                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
                memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
                       sizeof(tunnel->sock->sk_v6_daddr));
                memcpy(uaddr, &sp, len);
        } else if (tunnel->version == 3 && tunnel->sock->sk_family == AF_INET6) {
                struct sockaddr_pppol2tpv3in6 sp;

                len = sizeof(sp);
                memset(&sp, 0, len);
                sp.sa_family    = AF_PPPOX;
                sp.sa_protocol  = PX_PROTO_OL2TP;
                sp.pppol2tp.fd  = tunnel->fd;
                sp.pppol2tp.pid = pls->owner;
                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
                sp.pppol2tp.s_session = session->session_id;
                sp.pppol2tp.d_session = session->peer_session_id;
                sp.pppol2tp.addr.sin6_family = AF_INET6;
                sp.pppol2tp.addr.sin6_port = inet->inet_dport;
                memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
                       sizeof(tunnel->sock->sk_v6_daddr));
                memcpy(uaddr, &sp, len);
#endif
        } else if (tunnel->version == 3) {
                struct sockaddr_pppol2tpv3 sp;

                len = sizeof(sp);
                memset(&sp, 0, len);
                sp.sa_family    = AF_PPPOX;
                sp.sa_protocol  = PX_PROTO_OL2TP;
                sp.pppol2tp.fd  = tunnel->fd;
                sp.pppol2tp.pid = pls->owner;
                sp.pppol2tp.s_tunnel = tunnel->tunnel_id;
                sp.pppol2tp.d_tunnel = tunnel->peer_tunnel_id;
                sp.pppol2tp.s_session = session->session_id;
                sp.pppol2tp.d_session = session->peer_session_id;
                sp.pppol2tp.addr.sin_family = AF_INET;
                sp.pppol2tp.addr.sin_port = inet->inet_dport;
                sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
                memcpy(uaddr, &sp, len);
        }

        error = len;

        l2tp_session_put(session);
end:
        return error;
}

/****************************************************************************
 * ioctl() handlers.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. However, in order to control kernel tunnel features, we allow
 * userspace to create a special "tunnel" PPPoX socket which is used for
 * control only.  Tunnel PPPoX sockets have session_id == 0 and simply allow
 * the user application to issue L2TP setsockopt(), getsockopt() and ioctl()
 * calls.
 ****************************************************************************/

static void pppol2tp_copy_stats(struct pppol2tp_ioc_stats *dest,
                                const struct l2tp_stats *stats)
{
        memset(dest, 0, sizeof(*dest));

        dest->tx_packets = atomic_long_read(&stats->tx_packets);
        dest->tx_bytes = atomic_long_read(&stats->tx_bytes);
        dest->tx_errors = atomic_long_read(&stats->tx_errors);
        dest->rx_packets = atomic_long_read(&stats->rx_packets);
        dest->rx_bytes = atomic_long_read(&stats->rx_bytes);
        dest->rx_seq_discards = atomic_long_read(&stats->rx_seq_discards);
        dest->rx_oos_packets = atomic_long_read(&stats->rx_oos_packets);
        dest->rx_errors = atomic_long_read(&stats->rx_errors);
}

static int pppol2tp_tunnel_copy_stats(struct pppol2tp_ioc_stats *stats,
                                      struct l2tp_tunnel *tunnel)
{
        struct l2tp_session *session;

        if (!stats->session_id) {
                pppol2tp_copy_stats(stats, &tunnel->stats);
                return 0;
        }

        /* If session_id is set, search the corresponding session in the
         * context of this tunnel and record the session's statistics.
         */
        session = l2tp_session_get(tunnel->l2tp_net, tunnel->sock, tunnel->version,
                                   tunnel->tunnel_id, stats->session_id);
        if (!session)
                return -EBADR;

        if (session->pwtype != L2TP_PWTYPE_PPP) {
                l2tp_session_put(session);
                return -EBADR;
        }

        pppol2tp_copy_stats(stats, &session->stats);
        l2tp_session_put(session);

        return 0;
}

static int pppol2tp_ioctl(struct socket *sock, unsigned int cmd,
                          unsigned long arg)
{
        struct pppol2tp_ioc_stats stats;
        struct l2tp_session *session;

        switch (cmd) {
        case PPPIOCGMRU:
        case PPPIOCGFLAGS:
                session = sock->sk->sk_user_data;
                if (!session)
                        return -ENOTCONN;

                if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
                        return -EBADF;

                /* Not defined for tunnels */
                if (!session->session_id && !session->peer_session_id)
                        return -ENOSYS;

                if (put_user(0, (int __user *)arg))
                        return -EFAULT;
                break;

        case PPPIOCSMRU:
        case PPPIOCSFLAGS:
                session = sock->sk->sk_user_data;
                if (!session)
                        return -ENOTCONN;

                if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
                        return -EBADF;

                /* Not defined for tunnels */
                if (!session->session_id && !session->peer_session_id)
                        return -ENOSYS;

                if (!access_ok((int __user *)arg, sizeof(int)))
                        return -EFAULT;
                break;

        case PPPIOCGL2TPSTATS:
                session = sock->sk->sk_user_data;
                if (!session)
                        return -ENOTCONN;

                if (WARN_ON(session->magic != L2TP_SESSION_MAGIC))
                        return -EBADF;

                /* Session 0 represents the parent tunnel */
                if (!session->session_id && !session->peer_session_id) {
                        u32 session_id;
                        int err;

                        if (copy_from_user(&stats, (void __user *)arg,
                                           sizeof(stats)))
                                return -EFAULT;

                        session_id = stats.session_id;
                        err = pppol2tp_tunnel_copy_stats(&stats,
                                                         session->tunnel);
                        if (err < 0)
                                return err;

                        stats.session_id = session_id;
                } else {
                        pppol2tp_copy_stats(&stats, &session->stats);
                        stats.session_id = session->session_id;
                }
                stats.tunnel_id = session->tunnel->tunnel_id;
                stats.using_ipsec = l2tp_tunnel_uses_xfrm(session->tunnel);

                if (copy_to_user((void __user *)arg, &stats, sizeof(stats)))
                        return -EFAULT;
                break;

        default:
                return -ENOIOCTLCMD;
        }

        return 0;
}

/*****************************************************************************
 * setsockopt() / getsockopt() support.
 *
 * The PPPoX socket is created for L2TP sessions: tunnels have their own UDP
 * sockets. In order to control kernel tunnel features, we allow userspace to
 * create a special "tunnel" PPPoX socket which is used for control only.
 * Tunnel PPPoX sockets have session_id == 0 and simply allow the user
 * application to issue L2TP setsockopt(), getsockopt() and ioctl() calls.
 *****************************************************************************/

/* Tunnel setsockopt() helper.
 */
static int pppol2tp_tunnel_setsockopt(struct sock *sk,
                                      struct l2tp_tunnel *tunnel,
                                      int optname, int val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_DEBUG:
                /* Tunnel debug flags option is deprecated */
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Session setsockopt helper.
 */
static int pppol2tp_session_setsockopt(struct sock *sk,
                                       struct l2tp_session *session,
                                       int optname, int val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_RECVSEQ:
                if (val != 0 && val != 1) {
                        err = -EINVAL;
                        break;
                }
                session->recv_seq = !!val;
                break;

        case PPPOL2TP_SO_SENDSEQ:
                if (val != 0 && val != 1) {
                        err = -EINVAL;
                        break;
                }
                session->send_seq = !!val;
                {
                        struct pppox_sock *po = pppox_sk(sk);

                        po->chan.hdrlen = val ? PPPOL2TP_L2TP_HDR_SIZE_SEQ :
                                PPPOL2TP_L2TP_HDR_SIZE_NOSEQ;
                }
                l2tp_session_set_header_len(session, session->tunnel->version,
                                            session->tunnel->encap);
                break;

        case PPPOL2TP_SO_LNSMODE:
                if (val != 0 && val != 1) {
                        err = -EINVAL;
                        break;
                }
                session->lns_mode = !!val;
                break;

        case PPPOL2TP_SO_DEBUG:
                /* Session debug flags option is deprecated */
                break;

        case PPPOL2TP_SO_REORDERTO:
                session->reorder_timeout = msecs_to_jiffies(val);
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Main setsockopt() entry point.
 * Does API checks, then calls either the tunnel or session setsockopt
 * handler, according to whether the PPPoL2TP socket is a for a regular
 * session or the special tunnel type.
 */
static int pppol2tp_setsockopt(struct socket *sock, int level, int optname,
                               sockptr_t optval, unsigned int optlen)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int val;
        int err;

        if (level != SOL_PPPOL2TP)
                return -EINVAL;

        if (optlen < sizeof(int))
                return -EINVAL;

        if (copy_from_sockptr(&val, optval, sizeof(int)))
                return -EFAULT;

        err = -ENOTCONN;
        if (!sk->sk_user_data)
                goto end;

        /* Get session context from the socket */
        err = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (!session)
                goto end;

        /* Special case: if session_id == 0x0000, treat as operation on tunnel
         */
        if (session->session_id == 0 && session->peer_session_id == 0) {
                tunnel = session->tunnel;
                err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
        } else {
                err = pppol2tp_session_setsockopt(sk, session, optname, val);
        }

        l2tp_session_put(session);
end:
        return err;
}

/* Tunnel getsockopt helper. Called with sock locked.
 */
static int pppol2tp_tunnel_getsockopt(struct sock *sk,
                                      struct l2tp_tunnel *tunnel,
                                      int optname, int *val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_DEBUG:
                /* Tunnel debug flags option is deprecated */
                *val = 0;
                break;

        default:
                err = -ENOPROTOOPT;
                break;
        }

        return err;
}

/* Session getsockopt helper. Called with sock locked.
 */
static int pppol2tp_session_getsockopt(struct sock *sk,
                                       struct l2tp_session *session,
                                       int optname, int *val)
{
        int err = 0;

        switch (optname) {
        case PPPOL2TP_SO_RECVSEQ:
                *val = session->recv_seq;
                break;

        case PPPOL2TP_SO_SENDSEQ:
                *val = session->send_seq;
                break;

        case PPPOL2TP_SO_LNSMODE:
                *val = session->lns_mode;
                break;

        case PPPOL2TP_SO_DEBUG:
                /* Session debug flags option is deprecated */
                *val = 0;
                break;

        case PPPOL2TP_SO_REORDERTO:
                *val = (int)jiffies_to_msecs(session->reorder_timeout);
                break;

        default:
                err = -ENOPROTOOPT;
        }

        return err;
}

/* Main getsockopt() entry point.
 * Does API checks, then calls either the tunnel or session getsockopt
 * handler, according to whether the PPPoX socket is a for a regular session
 * or the special tunnel type.
 */
static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
                               char __user *optval, int __user *optlen)
{
        struct sock *sk = sock->sk;
        struct l2tp_session *session;
        struct l2tp_tunnel *tunnel;
        int val, len;
        int err;

        if (level != SOL_PPPOL2TP)
                return -EINVAL;

        if (get_user(len, optlen))
                return -EFAULT;

        if (len < 0)
                return -EINVAL;

        len = min_t(unsigned int, len, sizeof(int));

        err = -ENOTCONN;
        if (!sk->sk_user_data)
                goto end;

        /* Get the session context */
        err = -EBADF;
        session = pppol2tp_sock_to_session(sk);
        if (!session)
                goto end;

        /* Special case: if session_id == 0x0000, treat as operation on tunnel */
        if (session->session_id == 0 && session->peer_session_id == 0) {
                tunnel = session->tunnel;
                err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
                if (err)
                        goto end_put_sess;
        } else {
                err = pppol2tp_session_getsockopt(sk, session, optname, &val);
                if (err)
                        goto end_put_sess;
        }

        err = -EFAULT;
        if (put_user(len, optlen))
                goto end_put_sess;

        if (copy_to_user((void __user *)optval, &val, len))
                goto end_put_sess;

        err = 0;

end_put_sess:
        l2tp_session_put(session);
end:
        return err;
}

/*****************************************************************************
 * /proc filesystem for debug
 * Since the original pppol2tp driver provided /proc/net/pppol2tp for
 * L2TPv2, we dump only L2TPv2 tunnels and sessions here.
 *****************************************************************************/

#ifdef CONFIG_PROC_FS

struct pppol2tp_seq_data {
        struct seq_net_private p;
        unsigned long tkey;             /* lookup key of current tunnel */
        unsigned long skey;             /* lookup key of current session */
        struct l2tp_tunnel *tunnel;
        struct l2tp_session *session;   /* NULL means get next tunnel */
};

static void pppol2tp_next_tunnel(struct net *net, struct pppol2tp_seq_data *pd)
{
        /* Drop reference taken during previous invocation */
        if (pd->tunnel)
                l2tp_tunnel_put(pd->tunnel);

        for (;;) {
                pd->tunnel = l2tp_tunnel_get_next(net, &pd->tkey);
                pd->tkey++;

                /* Only accept L2TPv2 tunnels */
                if (!pd->tunnel || pd->tunnel->version == 2)
                        return;

                l2tp_tunnel_put(pd->tunnel);
        }
}

static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
{
        /* Drop reference taken during previous invocation */
        if (pd->session)
                l2tp_session_put(pd->session);

        pd->session = l2tp_session_get_next(net, pd->tunnel->sock,
                                            pd->tunnel->version,
                                            pd->tunnel->tunnel_id, &pd->skey);
        pd->skey++;

        if (!pd->session) {
                pd->skey = 0;
                pppol2tp_next_tunnel(net, pd);
        }
}

static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
{
        struct pppol2tp_seq_data *pd = SEQ_START_TOKEN;
        loff_t pos = *offs;
        struct net *net;

        if (!pos)
                goto out;

        if (WARN_ON(!m->private)) {
                pd = NULL;
                goto out;
        }

        pd = m->private;
        net = seq_file_net(m);

        if (!pd->tunnel)
                pppol2tp_next_tunnel(net, pd);
        else
                pppol2tp_next_session(net, pd);

        /* NULL tunnel and session indicates end of list */
        if (!pd->tunnel && !pd->session)
                pd = NULL;

out:
        return pd;
}

static void *pppol2tp_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
        (*pos)++;
        return NULL;
}

static void pppol2tp_seq_stop(struct seq_file *p, void *v)
{
        struct pppol2tp_seq_data *pd = v;

        if (!pd || pd == SEQ_START_TOKEN)
                return;

        /* Drop reference taken by last invocation of pppol2tp_next_session()
         * or pppol2tp_next_tunnel().
         */
        if (pd->session) {
                l2tp_session_put(pd->session);
                pd->session = NULL;
        }
        if (pd->tunnel) {
                l2tp_tunnel_put(pd->tunnel);
                pd->tunnel = NULL;
        }
}

static void pppol2tp_seq_tunnel_show(struct seq_file *m, void *v)
{
        struct l2tp_tunnel *tunnel = v;

        seq_printf(m, "\nTUNNEL '%s', %c %d\n",
                   tunnel->name,
                   tunnel->sock ? 'Y' : 'N',
                   refcount_read(&tunnel->ref_count) - 1);
        seq_printf(m, " %08x %ld/%ld/%ld %ld/%ld/%ld\n",
                   0,
                   atomic_long_read(&tunnel->stats.tx_packets),
                   atomic_long_read(&tunnel->stats.tx_bytes),
                   atomic_long_read(&tunnel->stats.tx_errors),
                   atomic_long_read(&tunnel->stats.rx_packets),
                   atomic_long_read(&tunnel->stats.rx_bytes),
                   atomic_long_read(&tunnel->stats.rx_errors));
}

static void pppol2tp_seq_session_show(struct seq_file *m, void *v)
{
        struct l2tp_session *session = v;
        struct l2tp_tunnel *tunnel = session->tunnel;
        unsigned char state;
        char user_data_ok;
        struct sock *sk;
        u32 ip = 0;
        u16 port = 0;

        if (tunnel->sock) {
                struct inet_sock *inet = inet_sk(tunnel->sock);

                ip = ntohl(inet->inet_saddr);
                port = ntohs(inet->inet_sport);
        }

        rcu_read_lock();
        sk = pppol2tp_session_get_sock(session);
        if (sk) {
                state = sk->sk_state;
                user_data_ok = (session == sk->sk_user_data) ? 'Y' : 'N';
        } else {
                state = 0;
                user_data_ok = 'N';
        }

        seq_printf(m, "  SESSION '%s' %08X/%d %04X/%04X -> %04X/%04X %d %c\n",
                   session->name, ip, port,
                   tunnel->tunnel_id,
                   session->session_id,
                   tunnel->peer_tunnel_id,
                   session->peer_session_id,
                   state, user_data_ok);
        seq_printf(m, "   0/0/%c/%c/%s %08x %u\n",
                   session->recv_seq ? 'R' : '-',
                   session->send_seq ? 'S' : '-',
                   session->lns_mode ? "LNS" : "LAC",
                   0,
                   jiffies_to_msecs(session->reorder_timeout));
        seq_printf(m, "   %u/%u %ld/%ld/%ld %ld/%ld/%ld\n",
                   session->nr, session->ns,
                   atomic_long_read(&session->stats.tx_packets),
                   atomic_long_read(&session->stats.tx_bytes),
                   atomic_long_read(&session->stats.tx_errors),
                   atomic_long_read(&session->stats.rx_packets),
                   atomic_long_read(&session->stats.rx_bytes),
                   atomic_long_read(&session->stats.rx_errors));

        if (sk) {
                struct pppox_sock *po = pppox_sk(sk);

                seq_printf(m, "   interface %s\n", ppp_dev_name(&po->chan));
        }
        rcu_read_unlock();
}

static int pppol2tp_seq_show(struct seq_file *m, void *v)
{
        struct pppol2tp_seq_data *pd = v;

        /* display header on line 1 */
        if (v == SEQ_START_TOKEN) {
                seq_puts(m, "PPPoL2TP driver info, " PPPOL2TP_DRV_VERSION "\n");
                seq_puts(m, "TUNNEL name, user-data-ok session-count\n");
                seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
                seq_puts(m, "  SESSION name, addr/port src-tid/sid dest-tid/sid state user-data-ok\n");
                seq_puts(m, "   mtu/mru/rcvseq/sendseq/lns debug reorderto\n");
                seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
                goto out;
        }

        if (!pd->session)
                pppol2tp_seq_tunnel_show(m, pd->tunnel);
        else
                pppol2tp_seq_session_show(m, pd->session);

out:
        return 0;
}

static const struct seq_operations pppol2tp_seq_ops = {
        .start          = pppol2tp_seq_start,
        .next           = pppol2tp_seq_next,
        .stop           = pppol2tp_seq_stop,
        .show           = pppol2tp_seq_show,
};
#endif /* CONFIG_PROC_FS */

/*****************************************************************************
 * Network namespace
 *****************************************************************************/

static __net_init int pppol2tp_init_net(struct net *net)
{
        struct proc_dir_entry *pde;
        int err = 0;

        pde = proc_create_net("pppol2tp", 0444, net->proc_net,
                              &pppol2tp_seq_ops, sizeof(struct pppol2tp_seq_data));
        if (!pde) {
                err = -ENOMEM;
                goto out;
        }

out:
        return err;
}

static __net_exit void pppol2tp_exit_net(struct net *net)
{
        remove_proc_entry("pppol2tp", net->proc_net);
}

static struct pernet_operations pppol2tp_net_ops = {
        .init = pppol2tp_init_net,
        .exit = pppol2tp_exit_net,
};

/*****************************************************************************
 * Init and cleanup
 *****************************************************************************/

static const struct proto_ops pppol2tp_ops = {
        .family         = AF_PPPOX,
        .owner          = THIS_MODULE,
        .release        = pppol2tp_release,
        .bind           = sock_no_bind,
        .connect        = pppol2tp_connect,
        .socketpair     = sock_no_socketpair,
        .accept         = sock_no_accept,
        .getname        = pppol2tp_getname,
        .poll           = datagram_poll,
        .listen         = sock_no_listen,
        .shutdown       = sock_no_shutdown,
        .setsockopt     = pppol2tp_setsockopt,
        .getsockopt     = pppol2tp_getsockopt,
        .sendmsg        = pppol2tp_sendmsg,
        .recvmsg        = pppol2tp_recvmsg,
        .mmap           = sock_no_mmap,
        .ioctl          = pppox_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl = pppox_compat_ioctl,
#endif
};

static const struct pppox_proto pppol2tp_proto = {
        .create         = pppol2tp_create,
        .ioctl          = pppol2tp_ioctl,
        .owner          = THIS_MODULE,
};

#ifdef CONFIG_L2TP_V3

static const struct l2tp_nl_cmd_ops pppol2tp_nl_cmd_ops = {
        .session_create = pppol2tp_session_create,
        .session_delete = l2tp_session_delete,
};

#endif /* CONFIG_L2TP_V3 */

static int __init pppol2tp_init(void)
{
        int err;

        err = register_pernet_device(&pppol2tp_net_ops);
        if (err)
                goto out;

        err = proto_register(&pppol2tp_sk_proto, 0);
        if (err)
                goto out_unregister_pppol2tp_pernet;

        err = register_pppox_proto(PX_PROTO_OL2TP, &pppol2tp_proto);
        if (err)
                goto out_unregister_pppol2tp_proto;

#ifdef CONFIG_L2TP_V3
        err = l2tp_nl_register_ops(L2TP_PWTYPE_PPP, &pppol2tp_nl_cmd_ops);
        if (err)
                goto out_unregister_pppox;
#endif

        pr_info("PPPoL2TP kernel driver, %s\n", PPPOL2TP_DRV_VERSION);

out:
        return err;

#ifdef CONFIG_L2TP_V3
out_unregister_pppox:
        unregister_pppox_proto(PX_PROTO_OL2TP);
#endif
out_unregister_pppol2tp_proto:
        proto_unregister(&pppol2tp_sk_proto);
out_unregister_pppol2tp_pernet:
        unregister_pernet_device(&pppol2tp_net_ops);
        goto out;
}

static void __exit pppol2tp_exit(void)
{
#ifdef CONFIG_L2TP_V3
        l2tp_nl_unregister_ops(L2TP_PWTYPE_PPP);
#endif
        unregister_pppox_proto(PX_PROTO_OL2TP);
        proto_unregister(&pppol2tp_sk_proto);
        unregister_pernet_device(&pppol2tp_net_ops);
}

module_init(pppol2tp_init);
module_exit(pppol2tp_exit);

MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("PPP over L2TP over UDP");
MODULE_LICENSE("GPL");
MODULE_VERSION(PPPOL2TP_DRV_VERSION);
MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_OL2TP);
MODULE_ALIAS_L2TP_PWTYPE(7);